linux-kernel - Re: [PATCH] ALSA: usb-audio: Don't refcount multiple accesses on the single clock

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Date:   Mon, 5 Sep 2022 14:06:45 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     alsa-devel@...a-project.org, LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Niklāvs Koļesņikovs 
        <89q1r14hd@...ay.firefox.com>, Wim Taymans <wtaymans@...hat.com>
Subject: Re: [PATCH] ALSA: usb-audio: Don't refcount multiple accesses on the
 single clock

On Mon, Sep 5, 2022 at 1:44 PM Takashi Iwai <tiwai@...e.de> wrote:
>
> On Mon, 05 Sep 2022 12:14:03 +0200,
> Jason A. Donenfeld wrote:
> >
> > This reverts commit 03a8b0df757f1beb21ba1626e23ca7412e48b525.
> > This reverts commit c11117b634f4f832c4420d3cf41c44227f140ce1.
> >
> > Pipewire and PulseAudio start devices with 44.1khz before changing them
> > to 48khz (or something different). By locking the rate, daemons are
> > unable to enumerate possible rates, and so they never change them to a
> > more optimal rate. This revert patch should allow 48khz audio again.
>
> Well, in that case, the revert is no right solution, IMO.
> If the patch caused a problem, it means that the application tries to
> change the rate while it's being still running by another.  If it
> worked, it worked just casually without noticing the bad behavior.

Not sure this is really what's happening. I think the issue is that
alsa reports that the device only supports a limited set of rates.
Pipewire then doesn't see 48khz, so it doesn't try to
stop,reclock,start.

Maybe Wim or Niklavs can provide more info about this.

Jason